Which one of the following is correct? Bengula current flows

1. Basics of Ocean Circulation: Forces and Factors (basic)

To understand how the vast oceans move, we must look at them not as static bodies of water, but as dynamic systems driven by a complex interplay of energy and physics. Much like rivers on land, ocean currents represent a regular volume of water moving in a definite path and direction FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Movements of Ocean Water, p.111. These movements are governed by two distinct sets of forces: Primary forces, which act as the 'engine' to initiate movement, and Secondary forces, which act as the 'steering wheel' or 'brakes' to influence the flow.

The movement begins with Solar Heating. As the sun heats the ocean surface, the water expands. This expansion is so significant that the sea level near the equator is approximately 8 cm higher than in the middle latitudes, creating a very slight gradient that causes water to flow down the slope FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Movements of Ocean Water, p.111. Simultaneously, Planetary Winds blow across the surface, using friction to drag the water along. Once the water is in motion, the Coriolis Force intervenes, deflecting the water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, ultimately forming large circular loops known as Gyres Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.487.

Force Category	Specific Factors	Role in Circulation
Primary Forces	Solar Heating, Wind, Gravity, Coriolis Force	Initiate the movement of water and determine its initial direction.
Secondary Forces	Temperature and Salinity differences	Influence the density of water, causing it to sink or rise (vertical movement).

While primary forces drive the surface, Secondary forces such as temperature and salinity dictate the 'density' of the water. Cold or highly saline water is denser and tends to sink, while warmer or fresher water remains buoyant. These differences create a vertical dimension to ocean circulation, ensuring that the ocean is a three-dimensional conveyor belt of heat and nutrients Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.487.

Sources: FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Movements of Ocean Water, p.111; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.486-487

2. Classification of Ocean Currents: Warm vs. Cold (basic)

To understand ocean currents, we must first look at them as the Earth's natural thermostat. The primary classification of currents into Warm and Cold is based on their temperature relative to the surrounding water and their direction of flow. At its simplest, if a current moves from the hot Equatorial regions toward the Poles, it is a Warm Current. Conversely, if it carries chilly water from the Polar regions toward the Equator, it is a Cold Current Certificate Physical and Human Geography, GC Leong, The Oceans, p.109.

This movement is driven by the principle of density. Cold water is denser and heavier, causing it to sink at the poles and move slowly toward the equator as a subsurface flow. To maintain equilibrium, lighter, warm surface water moves from the equator toward the poles FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI, Movements of Ocean Water, p.111. These currents act like massive conveyor belts that redistribute heat across the planet. Their placement along continental coasts follows a distinct geographical pattern due to the Earth's rotation and prevailing wind systems:

Latitude Region	West Coast of Continents	East Coast of Continents
Low & Middle Latitudes (Tropics/Subtropics)	Cold Currents (e.g., Canary, Benguela)	Warm Currents (e.g., Gulf Stream, Brazil)
High Latitudes (Sub-polar)	Warm Currents (e.g., North Atlantic Drift)	Cold Currents (e.g., Labrador, Oyashio)

The impact of these currents on local climate is profound. Warm currents raise the temperature of coastal areas and increase humidity, often leading to rainfall. Cold currents, however, lower the temperature of warm tropical regions and are frequently associated with desiccating (drying) effects, which is why many of the world's great deserts are located on the western margins of continents adjacent to cold currents FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI, Water (Oceans), p.103.

Sources: Certificate Physical and Human Geography, GC Leong, The Oceans, p.109; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI, Movements of Ocean Water, p.111; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, NCERT Class XI, Water (Oceans), p.103; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.488

3. The Global Gyre System (intermediate)

A Gyre is essentially a massive, circular system of ocean currents that rotates across an entire ocean basin. If you imagine the ocean as a giant engine, the gyres are the primary "gears" that keep the water moving globally. These systems are not random; they are closed-loop circuits formed by the delicate interplay of prevailing winds, the Coriolis effect, and the presence of continental landmasses that act as barriers Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.487.

There are five major subtropical gyres on Earth: the North and South Atlantic, the North and South Pacific, and the Indian Ocean gyre. Each is powered by the Trade Winds (blowing west near the equator) and the Westerlies (blowing east at higher latitudes). Because of the Coriolis effect, water is deflected to the right in the Northern Hemisphere (creating clockwise gyres) and to the left in the Southern Hemisphere (creating counter-clockwise gyres). A unique feature of these systems is the center of the gyre, such as the Sargasso Sea in the North Atlantic, which is a calm zone of relatively still water trapped within the swirling currents Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.487.

To understand a gyre, we look at its four distinct sides, which have a profound impact on regional climates. The Western Boundary Currents (like the Gulf Stream or Brazil Current) move warm water from the equator toward the poles along the east coasts of continents. Conversely, Eastern Boundary Currents (like the Canary or Benguela currents) bring cold water from the poles back toward the equator along the west coasts of continents FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Movements of Ocean Water, p.112.

Feature	Western Boundary Currents	Eastern Boundary Currents
Temperature	Warm (from Equator)	Cold (from Poles)
Coast Affected	East Coasts of Continents	West Coasts of Continents
Speed & Depth	Fast, deep, and narrow	Slow, shallow, and wide
Examples	Gulf Stream, Kuroshio, Brazil Current	California, Canary, Benguela Current

Sources: Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.487; FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.), Movements of Ocean Water, p.112; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.490

4. Connected Concept: Upwelling and Marine Productivity (intermediate)

To understand marine productivity, we must first look at the ocean as a layered system. In the sunlit surface layer (the photic zone), microscopic plants called phytoplankton thrive through photosynthesis. However, as these organisms and the animals that eat them die, their remains sink into the dark, deep ocean. This creates a dilemma: the sunlight is at the top, but the essential nutrients (like phosphates and nitrates) eventually settle at the bottom Environment and Ecology, Majid Hussain, MAJOR BIOMES, p.29. Upwelling is the vertical motion that solves this problem, acting as a 'nutrient elevator' that brings cold, mineral-rich water from the depths back to the surface.

This process is primarily driven by winds and the Coriolis effect. When steady winds blow parallel to a coastline, they push the surface water away from the shore (a process known as Ekman transport). To fill the resulting gap, cold water rises from below. This cold water is not just nutrient-rich; it often contains higher levels of CO₂ Environment, Shankar IAS Academy, Ocean Acidification, p.265. Once these nutrients reach the sunlit surface, they trigger a massive 'bloom' of phytoplankton, such as diatoms, which form the base of the entire marine food web Physical Geography by PMF IAS, Climatic Regions, p.465.

The impact of upwelling on global geography and economics is profound. Major upwelling zones are found along the eastern boundaries of oceans, such as off the coasts of Peru and Southwest Africa (the Benguela region). These areas become the world's most fertile fishing grounds because the abundance of plankton supports massive populations of fish Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.490. Additionally, productivity is high where cold and warm currents mix, such as the Grand Banks near Newfoundland, because the mixing replenishes oxygen and promotes plankton growth Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.497.

Sources: Environment and Ecology, Majid Hussain, MAJOR BIOMES, p.29; Environment, Shankar IAS Academy, Ocean Acidification, p.265; Physical Geography by PMF IAS, Climatic Regions, p.465; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.490; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.497

5. Connected Concept: Ocean Currents and Coastal Deserts (intermediate)

To understand why the world’s most iconic coastal deserts are located where they are, we must look at the cold ocean currents that wash against the western margins of continents. In the subtropical latitudes (roughly 20° to 30° North and South), cold currents like the Peruvian (Humboldt), Benguela, and California currents play a decisive role in suppressing rainfall. While we usually think of the ocean as a source of moisture, these cold waters act as a “moisture-blocker” for the adjacent land.

The primary reason for this aridity is a phenomenon called temperature inversion. When moist air moves over a cold ocean current, the lower layer of the air is chilled by the water. This creates a layer of cool, dense air trapped beneath a layer of warmer air. Since cool air is heavier, it refuses to rise; this prevents convection—the upward movement of air necessary for cloud formation and heavy rain. Instead of rain, these regions often experience thick advection fog or mist. As this air eventually moves inland over the hot desert soil, it warms up. This warming increases the air’s capacity to hold moisture, making it “thirsty” rather than “rainy,” a process known as the desiccating effect Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.496.

A classic example is the Atacama Desert in Chile, one of the driest places on Earth. The cold Peruvian Current chills the air so effectively that the mean annual rainfall is less than 1.5 cm Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.496. Similarly, the Namib Desert in Africa owes its existence to the Benguela Current, which flows northward along the southwest coast Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.493. These currents, combined with onshore winds, ensure that while the coast might be foggy and cool, the land remains parched and arid NCERT Class IX, Contemporary India-I, p.27.

Current Type	Atmospheric Impact	Coastal Result
Cold Currents (e.g., Benguela, Peru)	Creates Temperature Inversion; stable air.	Arid/Desert conditions, frequent fog, low rainfall.
Warm Currents (e.g., Brazil, Gulf Stream)	Encourages convection; unstable air.	Humid/Tropical conditions, high rainfall.

Sources: Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.493; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.496; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.499; NCERT Class IX, Contemporary India-I, Climate, p.27

6. Atlantic Ocean Currents Mapping (exam-level)

To understand the Atlantic Ocean's circulation, we must look at it as two giant subtropical gyres—one in the North and one in the South—separated by the Equator. These gyres are essentially massive circular patterns of water driven by the Trade Winds (near the Equator) and the Westerlies (in higher latitudes), modified by the Coriolis effect which deflects moving objects to the right in the North and to the left in the South.

In the North Atlantic, the circulation is clockwise. It begins with the North Equatorial Current, which is pushed westward by the Trade Winds. As it hits the landmass of the Americas, it moves north, becoming the famous Gulf Stream—one of the strongest warm currents in the world. This water eventually drifts toward Europe as the North Atlantic Drift. To complete the circle, the water turns south along the coasts of Spain and North Africa as the cold Canary Current Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.492. This loop traps a calm body of water in the middle known as the Sargasso Sea, famous for its distinct seaweeds.

The South Atlantic mirrors this but in an anti-clockwise direction. The South Equatorial Current flows from Africa toward Brazil, where it hits the protruding 'shoulder' of the continent at Cape Sao Roque. Here, the current bifurcates: a portion goes north to join the Caribbean system, while the main southern branch becomes the warm Brazil Current GC Leong, The Oceans, p.111. Upon reaching about 40° S, the Westerlies push the water eastward to merge with the West Wind Drift. This water eventually turns north along the southwestern coast of Africa as the Benguela Current.

The Benguela Current is particularly significant for geography students because it is a cold current that causes upwelling—where deep, nutrient-rich waters rise to the surface. This makes the waters off Namibia and South Africa exceptionally productive for fisheries but also contributes to the aridity of the nearby Namib Desert Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.493.

Feature	North Atlantic Gyre	South Atlantic Gyre
Direction	Clockwise	Anti-clockwise
Western Boundary (Warm)	Gulf Stream / Florida Current	Brazil Current
Eastern Boundary (Cold)	Canary Current	Benguela Current
Central Feature	Sargasso Sea	No distinct seaweed collection

Sources: Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.492-493; Certificate Physical and Human Geography, GC Leong, The Oceans, p.110-111

7. The Benguela Current System (exam-level)

The Benguela Current is a major cold ocean current that forms the eastern boundary of the South Atlantic subtropical gyre. It originates when the South Atlantic Current (a part of the West Wind Drift) reaches the southern tip of Africa and splits. One branch continues east, while the other turns northward, flowing along the west coasts of South Africa and Namibia Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p. 493. Eventually, this current moves toward the equator and merges with the South Equatorial Current, completing the counter-clockwise circulation (circuit) of the South Atlantic Physical Geography by PM=F IAS, Ocean Movements Ocean Currents And Tides, p. 491.

What makes the Benguela Current system exceptionally important is the phenomenon of coastal upwelling. As the current flows northward, the prevailing trade winds and the Earth's rotation (Coriolis effect) push the surface waters away from the African coastline. This allows deep, cold, and nutrient-rich waters to rise to the surface. These nutrients act as fertilizer for phytoplankton, creating a massive food base that supports some of the most productive commercial fisheries in the world. This is a common characteristic of eastern boundary currents, similar to the California Current or the Peru (Humboldt) Current.

To understand its geographical context, it is helpful to compare it with its neighbors. While the eastern side of the South Atlantic features the cold Benguela Current, the western side (along the coast of South America) is dominated by the warm Brazil Current. Similarly, on the opposite side of the African continent in the Indian Ocean, the Agulhas Current flows southward as a warm current Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p. 495. This contrast between the cold west coast and the warm east coast significantly influences the regional climates and marine biodiversity of Southern Africa.

Sources: Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.493; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.491; Physical Geography by PMF IAS, Ocean Movements Ocean Currents And Tides, p.495

8. Solving the Original PYQ (exam-level)

Now that you have mastered the dynamics of subtropical gyres and the classification of cold vs. warm currents, this question serves as a perfect application of those principles. To solve this, you must synthesize your knowledge of the South Atlantic Gyre. Specifically, remember that eastern boundary currents flow from high latitudes (the poles) toward the equator along the western edges of continents. The Benguela Current is the classic cold current that completes the South Atlantic loop by moving northward after branching off from the South Atlantic Current.

To arrive at the correct answer, visualize the map of Africa. As the westward-moving waters of the Southern Ocean hit the southern tip of the continent, a branch is forced northward. This current hugs the off South west African coast, specifically alongside South Africa and Namibia, before eventually merging with the South Equatorial Current. This process brings cold, nutrient-rich water to the surface through coastal upwelling, which is why the answer is (B). As highlighted in Physical Geography by PMF IAS, this current is a primary driver of the region's unique maritime climate and productive fisheries.

UPSC frequently uses geographical distractors to test whether you can distinguish between similar currents in different basins. Option (A) is a warm current (the Brazil Current) located on the opposite side of the same ocean. Options (C) and (D) are common traps involving other cold currents: the Canary Current flows off the North African coast, and the California Current borders the United States. The key to avoiding these traps is to always associate the current's name with its specific ocean basin and its position relative to the continental coastline.